Click on the "Quick Links" button at the top, then on the menu that drops down from that click "Edit Profile". When that pages loads click "Edit Avatar" - you then have to pick a picture from you computer (by clicking "browse") or enter the url (web address) of the image you want to use. The image can only be 80pixels wide by 80pixels high though. (I think the forum may shrink larger images to the right size, but cant remember)